Places a segment on an existing linear element. The new line will be placed on top of the existing linear element, but will start in the station specified by the from_station parameter and end in the station specified by the to_station parameter. Example: If the script is currently validating a 300 inch line string and the following command is used: PLACE SEGMENT 50 150, the result will be a segment that starts 50 inches from the start of the original line string (measured along the original element) and ends 150 from the start of the original element. If the to_station parameter is not specified, a zero length segment will be placed starting at the from_station.